I've done just that--but a bit higher than outlet height. I did it with Atlantic Technology in-wall speakers. The Atlantic tech speakers allow for a 20 degree adjustment on the tweeter, so what I did was deliberately install them upside down so that the tweeter would fire up instead of down. It's for just the type of scenario you're describing. The problem you get with in-walls is that the sound is emanating from only a single wall/location. With in-ceiling speakers you can make it more of an ambiance-thing. I've used Monoprice in-ceiling in my kitchen for a DIY installation I did several years ago.
So, to your point, yes, you can indeed do the installation. For ambiance, low music, it's not really a big deal. You're not going for high-fidelity. I wouldn't think twice about doing it and just put the speakers where you think they look best aesthetically.